1. Technical Field
The present disclosure relates to a starter to start an engine mounted on a vehicle, and more particularly to a starter adapted to an idle stop system of a vehicle.
2. Description of the Related Art
Recently, to reduce carbon dioxide emission and improve the fuel efficiency, vehicles provided with an idle stop system (hereinafter referred to ISS) that automatically stops and restarts the engine has been increased. In such vehicles, the starter is provided with an electromagnetic solenoid that integrates functions that the pinion is pushed out in response to a movement of the plunger, current flowing through the motor is enabled/disabled and rush current is suppressed when the motor is activated.
The conventional type starter to start the engine is not capable of restarting the engine until the engine is completely stopped when the idle stop function is performed, that is, the engine cannot be restarted while the engine is rotating by inertial rotation.
According to the conventional type starter, one solenoid switch (referred to non-ISS switch in this disclosure) controls the pinion to be pushed out towards the ring gear side of the engine and a main switch used to intermit the motor current to be ON and OFF.
Meanwhile, for example, Japanese Patent Application Laid-Open Publication No. 2011-144799 discloses a starter provided with a tandem solenoid switch (hereinafter is referred to ISS switch) which is capable of restarting the engine in response to an restart request by the driver. The ISS switch includes a solenoid SL1 used for pushing the pinion out and a solenoid SL2 used to open and close the main contact point and both solenoids are configured to be controlled individually. In other words, since the operation that the solenoid SL1 pushes the pinion out and the operation that the solenoid SL2 opens/closes the main switch can be controlled individually, even though the engine is rotating inertially, the engine can be restarted by engaging the pinion with ring gear.
Since vehicles having ISS stop the engine every time when the vehicle has to stop at an intersection due to a red signal or due to a traffic jam, and restart the engine in response to a restart request, the frequency of the engine start operation is significantly increased. In this respect, a problem arises that a large amount of current (referred to as starting current or rush current) flows when the motor is activated in response to the engine restart request after the idle stop operation is performed. Specifically, when a large amount of current flows, the terminal voltage of the battery is greatly decreased so that instantaneous power failure occurs in the vehicle, whereby electric equipment such as meters, audio equipment or a navigation system momentarily stop operation. Generally, since the vehicle provided with the ISS performs the idle stop on the road, a large amount of current flows every time when the starter operates so that the driver may be stressed significantly from this phenomena.
To avoid occurrence of the instantaneous power failure, a suppression resistor is employed. For example, Japanese Patent Application Laid-Open Publication No. 2011-142067 discloses a technique in which an electromagnetic relay (referred to ICR (In-rush current reduction) relay) that integrates a suppression resistor is connected to an activation circuit of the motor and a low resistance circuit path and a high resistance circuit path are controlled to be switched therebetween in response to the relay contact being ON and OFF. This ICR relay forms high resistor circuit path including the suppression resistor when the ICR relay is opened (turned OFF) in response to activation of the motor. As a result, suppressed current flows into the motor from the battery through the suppression resistor, whereby significant voltage drop at the terminal of the battery can be avoided. Subsequently, when the relay contact is closed (turned ON), both ends of the suppression resistor are short-circuited to form the low resistor circuit path, whereby the whole battery voltage is applied to the motor.
However, a conventional type switch used for the ISS individually controls each of the solenoids regardless of the sequence of operations thereof so that a large enough heat capacity that meets the rate of operation of the starter and its margin value are necessary for both solenoids SL1 and SL2. Hence, sizes of both solenoids become larger in order to secure heat resistance. Further, since the solenoids SL1 and SL2 are controlled by a vehicle side ECU (electronic control unit), two terminals (hereinafter is referred to terminal-50) are necessary to supply power to both solenoids SL1 and SL2. In other words, as shown in FIG. 16, the terminal-50 T1 for SL1 and the terminal-50 for terminal SL2 are disposed separately so that sizes of the terminal-50 T1 and the terminal-50 T2 become larger. Therefore, the mountability to the vehicle side is degraded and the system cost will increase since two harnesses and the starter relays which are connected to the terminal-50 T1 and T2 are required for the two terminals T1 and T2.
Moreover, to secure a performance of the engaging between the pinion and the ring gear as similar to that of the non-ISS switch, the current required to hold the plunger of the solenoid SL1 becomes larger compared to that of the non-ISS switch. Accordingly, depending on the type of vehicle, fuse capacity of the terminal-50 for the harness is required to be larger and wire diameter of the harness is required to be increased, thereby increasing the system cost of the ISS unit. Since the ICR relay conventionally used is an individual component, it is necessary to prepare a signal line in order to operate the ICR relay and a harness to connect the ICR relay and the starter, so that necessary man-hours and the number of components are increased, thereby increasing the system cost. Further, the ICR relay and the starter are connected by an additional harness whereby wiring resistance increases due to the additional harness. As a result, since the output power of the starter is decreased, depending on types of vehicles, it is necessary to use a starter having larger output power compared to conventionally used starters.
Furthermore, since a fixing portion to fix the ICR relay is required to be disposed in the starter housing or the vehicle side, depending on types of vehicles, the fixing portion may not be disposed in the vehicle. In FIG. 16, an example that the ICR relay is fixed to the starter housing 139 is illustrated. Specifically, the ICR relay is fixed to the starter housing 139 together with the ISS switch 120 by a bolt 140. When the ICR relay is required to be disposed at battery side with respect to the B terminal (i.e., a bolt to which the battery cable is connected) of the electromagnetic switch, voltage is always applied to the connection terminal of the ICR relay. Therefore, to avoid an unnecessary short circuit caused by a foreign body or a tool contacting to the connection terminal of the ICR relay, a protection cover is necessary to cover the connection terminal. As a result, necessary man-hour and the number of components are further increased so that the system cost will be increased.